Is the five second rule too strict?

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Are you questioning the five second rule for how long food can stay on the floor before it's inedible? Well, don't. That's disgusting. But the important thing is that science has put the rule to the test! Find out just how gross you've been, over the years, and how much it matters.


Plenty of people have heard of the 'five-second rule'. It is otherwise known as the 'I really want that cookie rule,' or as its variation, 'There's no other bread in the house and I'll be damned if I'm going to the corner store at this time of night rule.' (The latter one is a favorite of bloggers. I've heard.) It turns out that there have been many tests conducted on just this rule.

The first test involved E. coli bacteria, ceramic tiles, and gummy bears. It was a simple timed test to see if the gummy bears had picked up any bacteria at all after five seconds. They had. But was the relatively short time they'd been exposed to the bacteria a mitigating factor? What if they'd been on the floor an hour? A second series of tests picked up were the first left off. This one used slices of bread on surfaces contaminated with salmonella. Five seconds of exposure left the bread with between 150 and 8,000 bacteria. A minute left them with about ten times as much. So overall, there is value in snatching a piece of food off the floor as quickly as possible. Still, a minute is twelve times as long as five second, while the food had only picked up ten times the bacteria. Clearly there was a rush of bacteria the moment the food hit the floor.

But does this mean that the five-second rule, that savior of slobs everywhere, has to be abandoned? Single digit values of salmonella can infect human beings, but we generally don't move through a world that's heavily contaminated with harmful bacteria. The salmonella investigators checked the floor of their own lab and found it free of even a single bacterium of salmonella. They had to use deliberately contaminated surfaces.

A third group of investigators decided to forgo the lab and go straight to the college cafeteria. They dropped apple slices and skittles, to see the difference between dry food and sticky, wet food. What they found was a revelation. The apple slices didn't show harmful bacteria, or bacteria at all, until they were on the floor for a minute. The skittles were fairly clean until they'd been on the floor five minutes. The researchers did not see grounds to invalidate the five-second rule. In fact, they did suggest it be extended to thirty seconds.

But that's disgusting.

Image: HTO
Via NY Times, Science Blogs, and Baking Bites.




If I drop something, I won't let it lie there; but it's not like I'm counting seconds either. Big whoop if it has been on our relatively clean floor for 15-20 seconds...

There's crap everywhere. The digestive system is pretty good at filtering it out. Just because harmful bacteria enter your mouth doesn't mean you'll get sick. If that were the case we'd be sick all the time. Heck, my kids spent years putting crap in their mouths when they were toddlers. ;)

I think it's also very cultural. In my experience, North Americans have way lower thresholds for being grossed out by this sort of thing than most Europeans. Unlike many (most) Americans, Europeans don't reach for the hand sanitizer and alcohol swab at the drop of a hat. And many doctors would say that is a good thing. There's even a movement to ban hand sanitizer because it is simply making bacteria resistant.

Another factor is wearing shoes inside. In the US, most people wear their outdoor shoes in the home. In Scandinavia, Finland and most of East Asia most people don't. So dirt from the outside that sticks to the soles tends not to be dragged around the floor.

But I digress.